This application claims the priority benefit of Taiwan application serial no. 92106901, filed Mar. 27, 2003.
1. Field of Invention
The present invention relates to a light-emitting device and fabricating method thereof. More particularly, the present invention relates to an active matrix organic light-emitting device and fabricating method thereof.
2. Description of Related Art
An organic light-emitting device is a highly efficient semiconductor for converting electrical energy into photonic energy. The organic light-emitting device is commonly used as an indicator light, a display panel and an optical read/write head. Due to the special properties possessed by an organic light-emitting device including no viewing angle restriction, easy to manufacture, low production cost, high response speed, large operating temperature range and full colorization, the organic light-emitting device has been used as a display in many multi-media systems.
At present, the active matrix type of organic light-emitting device is being actively researched. An active matrix organic light-emitting device comprises an organic light-emitting layer and a cathode layer formed over a substrate having an array of thin film transistor thereon. The thin film transistors are the principal drivers for driving an active matrix light-emitting display device.
FIG. 1 is a schematic cross-sectional view of a conventional active matrix organic light-emitting device. To form the active matrix organic light-emitting device as shown in FIG. 1, a thin film transistor 130 is formed over a substrate 100. The thin film transistor 130 comprises a gate 102, a channel layer 106, an ohmic contact layer 108 and source/drain terminals 110a/110b. The gate 102 and the channel layer 106 are isolated from each other through a gate insulation layer 104.
Thereafter, an insulating layer 112 is formed over the substrate 100 covering the thin film transistor 130. A contact opening 114 is formed in the insulating layer 112. The contact opening 114 exposes the drain terminal 110b of the thin film transistor 130. An anode layer 116 is formed over the insulating layer 112 and the exposed opening 114. Finally, a light-emitting layer 118 is formed over the anode layer 116 and then a cathode layer 120 is formed over the light-emitting layer 118.
In the aforementioned method of fabricating the active matrix organic light-emitting device, it is difficult to form a light emitting layer 118 having an ideal coverage at the junction with the contact opening 114. Consequently, after the cathode layer 120 is formed over the light-emitting layer 118, the cathode layer 120 may form a short circuit with the anode layer 116 via the contact opening 114 leading to the production of dark lines on the display device and a shortening of its working life.
Moreover, the poor coverage of the light-emitting layer 118 is due to the formation of a large inverted angle at the junction between the anode layer 116 and the contact opening 114. Hence, the subsequent deposition of material over the anode layer 116 to form the light-emitting layer 118 is incomplete.
Accordingly, one object of the present invention is to provide an active matrix organic light-emitting device and fabricating method thereof that prevents a possible short-circuit between an anode layer and an cathode layer at a contact opening inside the device.
A second object of this invention is to provide an active matrix organic light-emitting device and fabricating method thereof that amends the problem of having an incompletely deposited light-emitting layer due to a large inverted angle at the junction between an anode and a contact opening inside the device.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of fabricating an active matrix organic light-emitting device. First, a switching device is formed on a substrate. The switching device is, for example, a thin film transistor comprising a gate, a channel layer formed over the gate, an ohmic contact layer formed over the channel layer and a source/drain region terminal formed over the ohmic contact layer. The gate and the channel layer are isolated from each other through a gate insulation layer. Thereafter, an insulating layer is formed over the substrate covering the thin film transistor. A contact opening is formed in the insulating layer to expose the drain terminal of the thin film transistor. An anode layer is formed over the insulating layer and the exposed contact opening. Next, a planarization layer is formed inside the contact opening. The planarization layer is formed, for example, by coating an organic photosensitive material layer over the anode layer globally and then performing a photolithographic process to pattern the organic photosensitive material layer. Hence, an organic photosensitive material layer is retained inside the contact opening to form the planarization layer. Finally, a light-emitting layer is formed over the anode layer and the planarization layer and then a cathode layer is formed over the light-emitting layer so that a complete active matrix organic light-emitting device is formed.
This invention also provides an active matrix organic light-emitting device. The active matrix organic light-emitting device comprises a switching device, an insulating layer, a contact, an anode layer, a planarization layer, a light-emitting layer and a cathode layer. The switching device is formed on a substrate. The switching device is, for example, a thin film transistor comprising a gate, a channel layer formed over the gate, an ohmic contact layer formed over the channel layer and a source/drain terminal formed over the ohmic contact layer. The gate and the channel layer are isolated from each other through a gate insulation layer. The insulating layer is formed over the substrate covering the thin film transistor. The contact is set up within the insulating layer. The contact is electrically connected to the drain terminal of the thin film transistor. The anode layer is formed over the insulating layer and is electrically connected to the contact. The planarization layer completely fills the space above the contact. The planarization layer is fabricated using an organic photosensitive material. The light-emitting layer is formed over the anode layer and the planarization layer. Furthermore, the cathode layer is formed over the light-emitting layer.
In this invention, organic photosensitive material is deposited into the contact opening to form the planarization layer after the anode layer is formed. Hence, the incomplete deposition of the light-emitting material is avoided. In other words, a possible short circuit between the anode layer and the cathode layer at the junction with the contact opening is prevented.
Furthermore, organic photosensitive material is deposited into the contact opening to form the planarization layer. Hence, an etching process is no longer needed. This reduces the risk of damaging the surface of the anode layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.